With the development of the technologies of wireless communication and information processing, portable electronic devices such as mobile telephones and electronic notebooks are now in widespread use. These electronic devices enable consumers to enjoy the convenience of high technology services anytime and anywhere. Foldable electronic devices are particularly welcome by consumers for their convenience.
Generally, foldable electronic devices have most of the electronics in one housing, called the main body. The other housing, called the flip cover, normally contains fewer electronic components than the main body. Other foldable electronic devices have all the electronics in the main body, with the flip cover containing no electronics. Various types of hinge assemblies are used to join a body and a cover of a foldable electronic device, so that the cover can unfold up from and fold down upon the body. Manufacturers are constantly seeking to reduce the volume, size and weight of portable radiotelephones. Thus, it is desirable that the hinge coupling the main body with the flip cover is modularized and miniaturized. A modularized hinge device has moving parts such as a cam member, a cam follower and a spring held together in a unified structure. The structure is easily and quickly attached to the main housing and the cover during mass production. A miniaturized hinge device has as few parts as possible, with the parts being as small as practicable.
One kind of hinge assembly employs a coil spring and a cam to make the flip cover open up from the main body and be held in an open position. An example of such kind of hinge assembly is disclosed in U.S. Pat. No. 6,085,387. The hinge assembly includes a can, a first member, a second member, and a spring. The can has a partially closed end and an open end. Two retaining protrusions are provided to close the open end by way of bending. The first member has a shaft protruding through the partially closed end of the can, and two protrusions defining a cam follower. The second member has a cam portion interacting with the cam follower. The cam portion includes at least a peak, two valleys separated by the peak, and slopes connecting the peak and the valleys. The spring pushes the second member toward the first member. The first member, the second member and the spring are contained within the can in turn. Then the protrusions are bent.
In the above-described hinge assembly, when the flip cover is only required to be opened to a small angle, the flip cover automatically rotates to a predetermined position by means of the engaging relationship of the cam follower of the first member and the cam portion of the second member. However, even though the movement track of the cam follower and the cam portion is the same when the mobile phone is opened or closed, the movement direction of the cam portion of the second member is contrary to that of the cam follower of the first member in both cases. This can result in excessive abrasion of elements of the hinge assembly, and thus reduce the effective working lifetime of the hinge assembly. In addition, the protrusions of the first member and the cam portions of the second member have symmetrically opposite configurations, so that the two steady positions of the flip cover are 180 degrees apart from each other. However, many mobile phones need to be opened to other positions such as 150 or 160 degree positions. This means that the body section of the mobile phone itself needs to be specially designed in order to limit the maximum opening angle of the flip cover. This takes up valuable “real estate” on the main body, and increases the complexity of manufacture of the main body. Furthermore, each time the flip cover is opened, it impacts the body section. The main body is liable to become worn or damaged, thereby shortening the working lifetime of the mobile phone. Moreover, a user must open the mobile phone with both hands. This makes the mobile phone awkward to utilize in situations when the user has only one hand free.
What is needed, therefore is to provide a new hinge assembly that overcomes the above-described problems.